1. Field of the Invention
This invention relates to positive clearance radial face seals for effecting a seal between relatively rotatable members, such as a shaft and a housing, to restrict or prohibit the leakage of a fluid from a first region at a relatively high pressure to a second region at relatively low pressure. The second region may be under vacuum, in which case the potential leakage may be from atmosphere to the vacuum region.
2. Description of the Prior Art
Positive clearance radial face seals are well known in the art and the technical problems involved in producing a satisfactory seal have been described in various papers including "Inherently stable high pressure face seals" by J. P. O'Donoghue and G. K. Lewis in (British Hydromechanical Research Association November 1969), and "A review of positive clearance radial face seals" by J. P. O'Donoghue (BHRA 1972).
Barrier or buffer face seals in which a buffer fluid is introduced into or extracted from the face seal at a point in the leakage path which would otherwise exist between the first and second regions, are also known. Such a barrier seal which ensures complete separation of the fluid to be sealed, for example for separating a toxic gas such as chlorine from the atmosphere, is described by H. Lindeboom in ASME Paper 67-PET-31 (September 1967).
Constructions of face seals are also described in British Pat. Specifications Nos. 1193,604 and 1263,693.
A face seal must have stability for satisfactory operation. A face seal operating by hydrostatic lift and using stepped or tapered face geometry to provide inherent stability of the clearance between the sealing faces of the seal has proved its practicability. Such face geometry has hitherto been provided by accurately machining a sealing face to a desired stepped or tapered configuration conforming to the operating conditions.